Since in the certification questions you have to choose the "best" option, I think the answer that is more accurate is C) Sequence Activities.
Even though all the responses are outputs of the time management knowledge area, the option "Sequence Activities" could be less invasive, since it consists of establishing the relations and order between the activities in the project schedule network diagram.
For the other part, defining activities, estimating activity resources, and estimating durations involve major changes in the respective project documents. Saving Changes...
